3com S7906E Manuel De Montage

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Configuration Prerequisites 
Before performing this configuration, complete the following configurations on the DHCP server: 
Enable DHCP 
Configure the DHCP address pool 
Enabling Unauthorized DHCP Server Detection 
Unauthorized DHCP servers may exist on networks, and they reply DHCP clients with wrong IP 
addresses. 
With this feature enabled, upon receiving a DHCP request, the DHCP server will record the IP address 
of the DHCP server which assigned an IP address to the DHCP client and the receiving interface. The 
administrator can use this information to check out any unauthorized DHCP servers. 
Follow these steps to enable unauthorized DHCP server detection: 
To do… 
Use the command… 
Remarks 
Enter system view 
system-view 
— 
Enable unauthorized DHCP 
server detection 
dhcp server detect 
Required 
Disabled by default. 
 
 
With the unauthorized DHCP server detection enabled, the device puts a record once for each DHCP 
server. The administrator needs to find unauthorized DHCP servers from the log information. 
 
Configuring IP Address Conflict Detection 
To avoid IP address conflicts, the DHCP server checks whether the address to be assigned is in use by 
sending ping packets. 
The DHCP server pings the IP address to be assigned using ICMP. If the server gets a response within 
the specified period, the server will select and ping another IP address; otherwise, the server will ping 
the IP addresses once again until the specified number of ping packets are sent. If still no response is 
received, the server will assign the IP address to the requesting client (The DHCP client probes the IP 
address by sending gratuitous ARP packets). 
Follow these steps to configure IP address conflict detection: 
To do… 
Use the command… 
Remarks 
Enter system view 
system-view 
— 
Specify the number of ping 
packets 
dhcp server ping packets 
number 
Optional 
One ping packet by default. 
The value 0 indicates that no ping 
operation is performed.